from ישעיהו מ יב (used in the haftara of Vaeschanan) is very familiar to me from prayers, and I can't think where it's from. Moreover, Google is not helping. Does anyone know where it's found in the prayers? (Not the daily or weekly prayers: it must be from some special-occasion prayer.)

Thank you!! It was driving me nuts, trying to remember. (I'd looked at Sh'kalim already, but didn't have, at hand, a version with the long piyut before k'dusha, so I thought it might be there, which is why I didn't mention my research and stop others from repeating it.)
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msh210♦Aug 14 '11 at 5:19